This invention relates to optical communications and more particularly to an encapsulated light source in which a fiberguide is coupled to a semiconductor light emitting device such as a junction laser.
In laser encapsulations containing a coupled fiberguide, it is important to secure the fiberguide in alignment with the laser chip so that minimal change in coupling can occur in use, and optimum light output to the transmission system is assured.
One practice used heretofore to couple an optical fiber to the output of a laser is to mount the end portion of the fiberguide in a precisely machined groove aligned with the laser. An arrangement of this type is disclosed in U.S. Pat. No. 3,774,987. Another technique, shown in U.S. Pat. No. 4,065,203, is to use a two-piece fiberguide coupling and to fix the innermost fiberguide portion in position with respect to the laser chip by the use of an epoxy cement.
The foregoing arrangements of the prior art have obvious shortcomings from the standpoint of ease and economy of manufacture, uniformity, stability, and reliability. The scheme in which the fiberguide is mounted in a groove, while suitable for the laboratory, is not a manufacturable structure which retains stability in field use in an optical communications system. The two-coupler arrangement also lacks the necessary assurance of accurate alignment and further does not provide long-term stability and reliability inasmuch as the organic materials used for affixing the fiberguide are very susceptible to creep, that is a change in dimension with time, even at room temperatures. Moreover, the high vapor pressure of such organic adhesives when used in an hermetic encapsulation result in the formation of unacceptable deposits on critical surfaces of the laser.
Accordingly, an object of this invention is a structure and a method for quickly and economically locking the end portion of a fiberguide to the light output of a laser in an hermetic encapsulation.
It is a further object of the invention to provide a fiberguide locking arrangement which has long-term stability and can be used without deleterious effect in an hermetic encapsulation.